Coldcard Hacker's Bitcoin Wallet Becomes Public Ledger

The Coldcard hacker's Bitcoin wallet has become an unlikely public canvas on the blockchain, receiving permanent messages since July 30. The wallet, holding around $36 million in stolen BTC, has been used to leave notes via OP_RETURN, a native protocol function that allows text to be attached to any transaction.

The mechanism behind this dynamic is OP_RETURN, originally designed for developers to timestamp documents or embed small proofs. However, the function also allows personal use, such as leaving notes directed at a specific address.

The messages tracked by Arkham Intelligence reveal a broad spectrum of intentions. Some are genuine pleas from victims, while others bear no relation to the theft whatsoever. One message offers BTC laundering services at a 10% fee and includes a Telegram username, betting on recruiting the hacker as a client.